633.平方数之和

class Solution {
    public boolean judgeSquareSum(int c) {
        long a = 0, b = (long)Math.sqrt(c);
        while(a <= b){
            long temp = a*a + b*b;
            if(temp > c) b--;
            else if(temp < c) a++;
            else return true;
        }
        return false;
    }
}